Process for the treatment of metals



Jan. 15, 1935. E, G. HERBERT 1,988,040

PROCESS FOR THE TREATMENT OF METALS Filed June 9. 1952 0 2 4 6 d l0 l2 20' www @M5-1mg# Patented Jan. 15, 193s 1,988,040

UNITED STATES PATENT OFFICE 1,988,040 n PnocEss Fon THE TREATMENT or METALS Edward Geisler Herbert, West Didsbury, Manchester, England Application June 9,1932, serial No. 616,175 In Great Britain June 22, 1931 8 Claims. (Cl. 148-40) This invention refers to a new or improved the application of the treatment, but its nal process for the secondary treatment of metals and hardness is usually less than the maximum and other substances inwhich iluctuations in their greater than the minimum which it has passed physical properties, such as hardness or ductilthrough in the course of its uctuations during ity, occur after a primary thermal, mechanical, or the period of ageing which intervenes between 5 magnetic treatment. the original treatment and the condition of sta- It has been discovered that metals which have bility. l undergone certain thermal or mechanical treat- It is-now found that as regards their immediate ments exhibit a series 4of periodic changes of and/or ultimate physical properties, the sub- 10 hardness during a period of ageing immediately stances subject to the aforesaid fluctuations of 10 following the treatment, the hardness changes bephysical properties respond to a further or secing associated with changes of other physical yondary magnetic treatment dilerently at dilferproperties such as ductility. The fluctuations of ent stages of their aforesaid uctuations. hardness consist or alternate increases and de- 'I'he object of this invention is to take advancreases, the periodicity of the fluctuations genertage of such discovery as regards the effect of 15 ally tending to increase, so that the rst change, the further or secondary treatment, to accentuate which may be either an increase or a decrease or decrease one or more of the physical proper- 'of hardness, may occupy only a few minutes, and ties of the substance beyond the limits otherwise later changes will usually occupy many hours. obtainable,inorder to obtain an optimum state of In some cases the lirst change occupies three or hardness for the particular purpose in hand. 20 four hours or longer, and subsequent changes gen- The present invention consists in applying to erally occupy longer periods. It is believed that the substance ata selected phase of its iiuctuathis phenomenon is not peculiar to metals, but tions a secondary magnetic treatment, such. as that it takes place in some other crystalline subwill stabilize the metal in the condition it has stances. then reached, or will influence the subsequent 25 The treatment which gives rise to these, fluctuiiuctuations in such a manner as may be desired. ations may be thermal, such as quenching from a In cases where the uctuations resulting from high temperature, or heating, or annealing, or it the primary treatment of metal have damped out,- may be mechanical such as rolling or hammering, the invention also consists in first reinstating or bombardment with steel balls. them by a primary treatment consisting in ro- 30 It has been discovered further that the changes tating the metal in a strong magnetic eld and of hardness of a metal set up by the'magnetic then applying the secondary treatment at the treatment, (generally consisting of rotation in a selected phase. magnetic field) described in my application of The terms primary treatment and Secondary prior date No. 474,309, led 9th August, 1930, are treatment are used in a relative sense, the prig5 also periodic fluctuations. It is believed that the mary treatment being that which causes the ilucperiodic fluctuations set up by thermal, mechanituations of hardness, and the secondary treat-` cal and magnetic treatments are essentially simiment that which stabilizes them. lar in character, and the hypothesis has been ad- The secondary treatment may consist of the 4o vanced that they are due to precessionin the sysapplication of a stationary magnetic eld, or a 40 tems Of electrons giving vrise to uctuations in rotating magnetic eld,orademagnetizing procmolecular cohesion. ess as hereinafter explained, and it may be ap- When the hardness fluctuations damp out they plied either to magnetic or non-magnetic metals, generally leave themetal with physical properat any selected phase of uctuations set up by 4,5 ties dilerent from those which it possessed imprevious thermal, mechanical, or magnetic dismediately after the treatment (thermal, mechanturbance, according t0 the result desired- While ical or magnetic) which gave rise to the uctuan important practical application of the Secondations. Thus, steel which has been quenched ary treatment is that of improving the physical from a high temperature, or annealed at a low properties of hard Steel used in cutting tools and temperature after having been work hardened, other structures and of improving the physical 59 or which has been hardened by cold working or characteristics of unhardened steels used for memagnetically treated according to my said patent chanical structures, it is to be particularly noted application No. 474,309, usually reaches stability that both the primary and secondary magnetic in a condition of hardness considerably higher treatments have been found effective when apthan that which it possessed immediately after plied to non-magnetic metals, Such as brass, and 55 that known by the registered Trade Mark Duralumin, and may be applied also to non-metallic bodies whose electronic systems are susceptible to the influence of magnetic elds.

An example of the carrying out of the invention is in the treatment of a steel wire which has been treated by rotating it in a magnetic field according to my patent application No. 474,309, and which after such treatment would normally pass through a series of hardness uctuations characterized by a maximum hardness immediately after treatment, a minimum 1/2 hour after, a maximum 11A? hours after, a minimum 5 hours after, and a maximum 12 hours after the magnetic treatment. Instead of permitting this normal course of uctuations, I select a particular phase such as the 11A hour maximum, or the 5 hour minimum, and at that particular period of the ageing process I subject the steel to a secondary treatment by placing it in a constant magnetic eld for several minutes, or as long as may be found eifective, or by a de-magnetizing process, the result of this treatment being to stabilize the metal in the physical condition which it has attained when the secondary treatment is applied.

Another example of the carrying out of the invention is in the treatment of a steel which has been hardened by quenching and which normally would pass through fluctuations of hardness such that the hardness reaches a maximum 3 hours after quenching and a minimum 7 hours after quenching. Instead of permitting this course of fluctuations, I select a particular phase such as the 3 hour maximum and at that phase subject the steel to a secondary treatment by placing it in a constant and stationary magnetic eld for a period of, say 2 minutes. The effect of this is found to be either a stabilization of the steel in the condition of. maximum hardness which it had attained when the secondary treatment was applied, or, more frequently, to cause an immediate further increase of hardness and some fluctuations of hardness which eventually damp out leaving the metal in a stable condition characterized by greater hardness than it possessed when the secondary treatment was applied.

The diagrams shown in the accompanying drawing represent the hardness time curves of specimens referred to in the following examples of carrying out the invention.

A razor blade was treated primarily by rotation in a magnetic field with the result that the hardness fell immediately and then rose considerably, ultimately (after 20 hours) falling to its original level. Fig. 1 is a graph of the test.

Another razor blade was similarly treated, but at the end of two hours a secondary magnetic treatment was applied to the blade by placing it in a stationary magnetic field for minutes. The result was an immediate rise in hardness, and a further progressive rise during 25 hours, the nal hardness being much higher than the previous maximum. Fig. 2 illustrates the changes of hardness.

Further consideration of the eects produced by the secondary treatment in a constant magnetic field, and especially of the fact that in some cases the constant eld does not immediately stabilize but sets up new fluctuations of a some- Y what Violent character and of shorter time magnetizing process. This would usually consist in rotating the substance in a strong magnetic eld and gradually withdrawing it from the iniiuence of the eld or alternatively, rotating the substance in a strong magnetic field, and gradually weakening the eld to zero, or as a further alternative, simultaneously reversing and weakening the field, the eiect in each case being to set up changes of polarity of gradually decreasing intensity so as finally to leave the substance magnetically neutral. Other demagnetizing processes such as an alternating magnetic eld may be employed. Where the secondary treatment results in new fluctuations, a second stabilizing treatment may be given at a selected phase of such new fluctuations.

Fig. 3 illustrates the hardness changes in a razor blade treated as in the previous examples, except that the secondary treatment was for 1 minute only, and subjected to a second stabilizing treatment after passing the induced maximum.

Fig. 4 illustrates the comparative hardness of two pieces of steel wire, each treated in a magnetic eld (by being given one turn in forty seconds) and one allowed to age normally as shown by the dotted graph, and the other stabilized by a secondary magnetic treatment for one minute and demagnetized, as shown by the full line graph.

'Ihe secondary treatment sometimes results in an immediate decrease in hardness, followed by a, rise to a maximum higher than that which preceded the secondary treatment. Fig. 5 illustrates such a change which took place in a specimen of Cobalt high speed steel stabilized by treatment for 3 minutes in a stationary eld.

Similarly, if a phase of minimum hardness is selected for the secondary treatment, the metal being placed in the constant magnetic eld at that phase of its fluctuations, the eiect will usually be an immediate decrease of hardness below the selected minimum, and certain fluctuations which eventually damp out leaving the metal less hard than when the secondary treatment was applied. See the graph in Fig. 6.

It will be understood that a change of hardness is always associated with changes in other physical properties such as ductility, and the purpose of the secondary treatment will often be to induce some useful physical property in the metal, of which the hardness change is y merely a sympton.

Brass has been stabilized by treatment in a ileld of 23,000 gauss strength.

In the case of the secondary magnetic treatment, it may be carried out by apparatus consisting of a two-part table connected with and forming extensions of the poles of the magnet. The parts of the table are adjustable and reversible and are each shaped so that diierent strengths and distributions of the magnetic eld are thereby obtainable, the substance to be treated being placed across the gap between the two parts of the table. Further, the magnet will preferably be designed so as to provide either a rotating magnetic field, or a constant magnetic eld or a de-magnetizing field.

What I claim is:-

l1. The process of producing an optimum state of hardness in metals, which consists in subjecting the metals to a primary treatment to produce periodic increase and decrease of hardness, in observing by means of a hardness testing instrument the fluctuations of hardness following such treatment, in selecting a phase of fluctuation for a secondary treatment, the selection being governed by the relationship of the desired optimum hardness to the initial hardness set up by the primary treatment, and in applying a secondary treatment at such selected phase by placing the metals in a locally generated magnetic field to stabilize the fluctuations.

v 2. The process claimed in claim 1 wherein the secondary treatment is eiected by placing the metal in the locally generated magnetic eld at a selected maximum phase of hardness uctuation,4 to produce a stabilized ultimate condition of hardness higher than that immediately preceding the secondary treatment.

3. The processv claimed in claim 1, wherein the secondary treatment is effected by placing the metal in the locally generated magnetic field at a selected minimum phase of hardness uctuation to produce a stabilized ultimate condition of hardness lower than that immediately preceding the secondary treatment.

4. The process of producing anoptimum state of hardness in metals, which consists in subjecting the metals to a primary hardening treatment, in observing by means of a hardness testing instrument the iiuctuations of hardness following such-treatment, in selecting a particular phase of.

fluctuation for a secondary treatment and in applying a secondary treatment at such selected phase by placing the metals in a locally generated constant magnetic eld to stabilize the uctuations.

5. The process of producing an optimum state of hardness in ferrous metals, which consists in subjecting the metals to a primary hardening treatment, in observing by means of a hardness testing instrument the fluctuations of hardness following such treatment, in selecting a particular phase of iiuctuation for a secondary treatment and in applying a secondary treatment at such selected phase by placing the metals in a locally generated constant rotating magnetic eld to stabilize the fluctuations.

6. The process of producing an optimum state of hardness in ferrous metals, which consists in subjecting the metals to a primary hardening treatment, in observing by means of a hardness testing instrument the fluctuations of hardness following such treatment, in selecting a particular phase of fluctuation for a secondary treatment and in applying a secondary treatment at such selected phase by subjecting the metals to the demagnetizing inuence of a locally generated variable magnetic eld to stabilize the fluctuations.

7. The process claimed in claim 1 charac terized by the further steps of observing fluctua tions set up by the secondary treatment, selecting a particular phase of such new uctuations and applying a second stabilizing treatment by again placing the metal within a locally generated magnetic eld.

8. The process claimed in claim 1 wherein the primary treatment consists in placing the metal within a locally generated magnetic field to produce fluctuations of hardness.

EDWARD GEISLER HERBERT. 

